Okay step away from the waving hands and read the source material.
The distribution of human lives versus years lived by humans will skew earlier, because infant mortality was absurd for the first two tranches, with something like 50% of people dying before the age of five, so it will be more like 40-40-20 over those time periods.
before 8000 BCE: ~9.0 billion births, 8% 8000 BCE–1650 CE: ~85.4 billion, 73% after 1650: ~22.6 billion, 19%
Looks also different to OPs website